1. Field of the Invention
The present invention relates to an information recording medium, a recording apparatus, a reproduction apparatus, a recording method, and a reproduction method, providing improved information reliability. More specifically, the present invention relates to an information recording medium, a recording apparatus, a reproduction apparatus, a recording method, and a reproduction method, allowing for updating of a defect list having a size of 2ECC (Error Correction Code) or larger and deletion of a defect entry.
2. Description of the Related Art
Recently, large capacity replaceable information recording media and disc drive apparatuses for driving such information recording media are becoming more and more popular. As large capacity replaceable information recording media, optical discs such as, for example, DVDs (Digital Versatile Discs) are well known. A disc drive apparatus irradiates an optical disc with laser light and thus forms very small pits in the optical disc so as to record information. The disc drive apparatus also irradiates an optical disc with laser light and reproduces a change in the reflectance caused by the pits as information. Large capacity replaceable information recording media are suitable to a disc drive apparatus performing information recording and reproduction in this manner. However, since the optical discs are replaceable, a defect caused by dust or scratches may exist on a recording surface thereof.
In order to guarantee the reliability of information recorded or reproduced by the disc drive apparatus, it is necessary to perform defect management of managing a defect existing on the optical disc. The defect management used for a conventional disc drive apparatus is described in the physical standards of DVD-RAM (e.g., “DVD Specifications for Rewritable Disc (DVD-RAM) Part 1 PHYSICAL SPECIFICATIONS Version 2.0”; hereinafter, referred to as the “DVD-RAM Standards”). Chapter 5 of the DVD-RAM Standards includes a description on the layout of a disc.
FIG. 12 shows a data structure of an information recording medium 1200 according to the DVD-RAM Standards.
The information recording medium 1200 includes a lead-in area 1201 for recording information regarding the disc, a data area 1202 for recording user data, and a lead-out area 1203 showing the termination position of the user data.
The lead-in area 1201 includes DMA1 (Defect Management Area) and DMA2 for recording defect management information used for managing a defect area existing in the data area 1202, and reserved areas 1204 and 1205 for future expansion.
The data area 1202 includes a user area 1206 for recording user data and a spare area 1207. When there is a defect area in the user area 1206, the user data which is to be recorded in the defect area is recorded in the spare area 1207 instead of a portion of the user area 1206 corresponding to the defect area.
The lead-out area 1203 includes DMA3 and DMA4 for recording defect management information used for managing a defect area existing in the data area 1202, and reserved areas 1208 and 1209 for future expansion, like the lead-in area 1201.
DMA1 through DMA4 have the same defect management information recorded in multiplex. The reason for this is that the information recorded in DMA1 through DMA4 cannot be a target of defect management. Even if some of DMA1 through DMA4 have a defect area and the information recorded on the information recording medium cannot be reproduced, as long as at least one of DMA1 through DMA4 is defect-free, the defect management information recorded in that area can be normally reproduced. Accordingly, loss of user data is prevented, which improves reliability.
DMA1 includes a DDS (Data Definition Structure) 1210, a PDL (Primary Defect List) 1211, and an SDL (Secondary Defect List) 1212.
The DDS 1210 includes information regarding a partition defining the PDL 1211 and the SDL 1212.
The PDL 1211 is position information (list) of defect areas (for example, defect sectors) detected in the user area 1206 and the spare area 1207 at the time of shipping of the information recording medium, i.e., at the time of initialization of the information recording medium. This list basically does not change unless the information recording medium is subjected to physical formatting.
According to the DVD-RAM Standards, the total size of the DDS 1210 and the PDL 1211 fits in one ECC (Error Correction Code) block. The size of the SDL 1212 also fits in one ECC block. An ECC block is a unit of error correction in DVD-RAM, and has a size of 32 kbytes in 16 sectors (each sector has a size of 2 kbytes). This size of one ECC block will be referred to as “1ECC size”.
FIG. 13 shows a detailed data structure of the SDL 1212.
Unlike the PDL 1211, the SDL 1212 is information (list) which changes when a defect area (for example, defect sector) is detected during recording or reproduction. When a defect area is detected, the SDL 1212 is written in each of DMA1 through DMA4 at a timing appropriate to the disc drive apparatus used.
The SDL 1212 includes a header 1301, a first defect entry 1302, a second defect entry 1303, . . . , an Nth defect entry 1304, and an unused area 1305.
The header 1301 includes, for example, an identifier which represents that the area is the SDL 1212, the total number of defect entries (N in the case of FIG. 13), and the number of times the SDL 1212 has been updated.
The first defect entry 1302 includes first defect position information 1306 showing the position of a defect area existing in the user area 1206 and first substitute position information 1307 showing the position of a part of the spare area 1207 in which the user data has been recorded instead of the defect area (for example, a substitute sector). The second defect entry 1303 includes second defect position information and second substitute position information. The Nth defect entry includes Nth defect position information and Nth substitute position information. Each of the defect position information and the substitute position information is generally a sector number.
The unused area 1305 exists in the case where the total size of the header 1301 and the first through Nth defect entries 1302 through 1304 is less than 1ECC size. In this case, padding data (for example, 0) which is meaningless information is recorded in the unused area 1305.
There is a risk that while the disc drive apparatus is writing the SDL 1212 in DMA1 through DMA4 of the information recording medium 1200, the power of the disc drive apparatus may be turned off and processing may be interrupted. In such a case, the disc drive apparatus determines the update result of the defect management areas (DMA1 through DMA4) by the following procedure.
(1) Error correction is performed on the SDL 1212 having 1ECC size. When the error correction is accurately performed, the SDL 1212 is determined to have been updated normally.
(2) The step of (1) is performed on all the SDLs included in DMA1 through DMA4.
(3) Regarding all the SDLs determined to have been updated normally in step (2), the numbers of updates of the SDLs included in the header are compared with one another. The SDL having the largest number of updates is determined to be the correct SDL (latest SDL).
As described above, when the size of the SDL 1212 is 1ECC size, the determination of the correct SDL can be performed accurately even when the power of the disc drive apparatus is turned off. Thus, the reliability of user data is guaranteed with no user data being lost.
Recently, as the amount of information to be recorded on information recording media is increased, high density recording technology and large capacity technology have remarkably improved. For example, using blue lasers, information recording media having a larger capacity than that of conventional optical discs are now under development. Since such an information recording medium allows a larger capacity of information to be recorded thereon, the size of the SDL is larger than 1ECC size. As long as the size of the SDL is 1ECC size or smaller as according to the DVD-RAM Standards, no problem arises. When the size of the SDL exceeds 1ECC size, the following problems occur. In the following case, the size of the SDL is assumed to be 4ECC size.
It is assumed that the following occurs to one DMA (for example, DMA1) as a result of the size of the SDL becoming 4ECC size instead of the conventional 1ECC size.                The header is completely updated.        The SDL is updated up to 2ECC blocks, and the power of the disc drive apparatus is turned off exactly when the third ECC block is starting to be updated.        
In this case, according to the conventional method of determining the SDL update result, error correction in units of 1ECC is normally performed. Comparing the number of updates of the SDL in DMA1 with that of the SDLs in DMA2 through DMA4, the number of updates of the SDL in DMA1 is maximum. Therefore, although the updating of the SDL in DMA1 fails in the middle, the SDL in DMA1 is erroneously determined to be the normal, latest SDL.
One solution proposed to solve this problem is to add a header for each ECC block of the SDL having 4ECC size. Each header includes, for example, an identifier which represents that the area is the SDL, the total number of defect entries, and the number of updates of the SDL.
FIG. 14 shows a data structure of an SDL 1400 having 4ECC size.
The SDL 1400 includes a first ECC block 1401, a second ECC block 1402, a third ECC block 1403, and a fourth ECC block 1404.
The first ECC block 1401 includes a header 1405, a first defect entry 1406, a second defect entry 1407, . . . , an (M−1)th defect entry 1408, and an Mth defect entry 1409.
The second ECC block 1402 includes a header 1410, an (M+1)th defect entry 1411, . . . , an Nth defect entry 1412, and an unused area 1413.
The third ECC block 1403 includes a header 1414 and an unused area 1415.
The fourth ECC block 1404 includes a header 1416 and an unused area 1417.
The headers 1405, 1410, 1414 and 1416 each include, for example, an identifier which represents that the area is the SDL, the total number of defect entries, and the number of updates of the SDL. The first through Nth defect entries 1406 through 1409, 1411 and 1412 each include defect position information and substitute position information. In the unused areas 1413, 1415 and 1417, padding data (for example, 0) which is meaningless information is recorded.
In this case, the disc drive apparatus determines the update result of the defect management areas (DMA1 through DMA4) by the following procedure.
(1) For the SDL 1400 having 4ECC size, error correction is performed on the first ECC block 1401. When the error correction is accurately performed, the first ECC block 1401 is determined to have been updated normally. This step is performed on the second through fourth ECC blocks 1402 through 1404 in the SDL 1400. When the error correction on the first through fourth ECC blocks 1401 through 1404 is accurately performed, the step (2) is performed.
(2) The numbers of updates of the headers 1405, 1410, 1414 and 1416 respectively added to the first through fourth ECC blocks 1401 through 1404 are compared with one another. When the numbers of updates of the headers 1405, 1410, 1414 and 1416 are all of the same value, the SDL 1400 is determined to have been updated normally.
(3) Steps (1) and (2) are performed on all the SDLs in DMA2 through DMA4.
(4) Regarding the SDLs determined to have been updated normally in step (3), the numbers of updates of the SDLs included in the header are compared with one another. The SDL having the largest number of updates is determined to be the correct SDL (latest SDL).
As described above, when the size of the SDL 1400 exceeds 1ECC size, a header is provided for each 1ECC block of the SDL, so that the correct SDL can be determined even when the power of the disc drive apparatus is turned off. Thus, the reliability of user data is guaranteed with no user data being lost.
There is another conventional technology for improving the reliability of data (see, for example, Japanese Laid-Open Publication No. 8-293187).
FIG. 15 shows a data structure of another conventional information recording medium 1500.
The structure of the information recording medium 1500 is identical with the structure of the information recording medium 1200 except for the structure of an SDL 1501 and except that the size of the SDL 1501 is not limited to 1ECC size. Regarding FIG. 15, identical elements previously discussed with respect to FIG. 12 bear identical reference numerals and the detailed descriptions thereof will be omitted.
The SDL 1501 includes a defect list identifier 1502 which represents that the area is the SDL 1501, a reserved field 1503 for future expansion, first update information 1504 and second update information 1510 for determining whether defect management information is old or new, a registered defect number 1505 which represents the number of defect sectors registered in the SDL 1501, first defect position information 1506 and second defect position information 1508 which represent the position of a defect sector, first substitute position information 1507 and second substitute position information 1509 which represent the position of a substitute sector for substituting the defect sector, and an unused field 1511 for registering defect sectors which may be detected in the future. The first update information 1504 and the second update information 1510 are, for example, numbers of times of recording. As long as the SDL 1501 is updated normally, the content of the first update information 1504 and the content of the second update information 1510 are identical to each other.
In this case, the disc drive apparatus determines the update result of the defect management areas (DMA1 through DMA4) by the following procedure.
(1) Regarding the SDL 1501, the content of the first update information 1504 and the content of the second update information 1510 are compared with one another. When the content of the first update information 1504 and the content of the second update information 1510 are identical to each other, the SDL 1501 is determined to have been updated normally.
(2) Step (1) is performed on all the SDLs in DMA2 through DMA4.
(3) Regarding the SDLs determined to have been updated normally in step (2), the contents of the update information in the SDLs are compared with one another. The SDL having the largest amount of update information is determined to be the correct SDL (latest SDL).
As described above, as long as the first update information and the second update information added to the SDL included in one of DMA1 through DMA4 are correctly read, the determination of the correct SDL can be performed accurately, regardless of the size of the SDLs.
However, the SDL 1400 shown in FIG. 14 has the following problems. A header needs to be added to all of the four ECC blocks included in the SDL 1400. This lowers the processing efficiency of updating the SDL 1400. In addition, a header (for example, the header 1410) is provided between one defect entry (for example, the Mth defect entry 1409) and another defect entry (for example, the (M+1)th defect entry 1411). Due to this structure, the operations of, for example, searching for, adding, and deleting a defect entry are complicated.
The information recording medium 1500 shown in FIG. 15 has the problem that the second update information 1511 may not be correctly read.
FIG. 16 shows data structures of defect lists in various states of the SDL 1501 in the information recording medium 1500 shown in FIG. 15. Part (a) shows a data structure of a pre-update defect list. Part (b) shows a data structure of a defect list which was updated normally. Part (c) shows a data structure of a defect list which was not updated normally. With reference to FIG. 16, how the SDL 1501 is updated, in the case where a sector which was previously determined as being registered as a defect area and then determined as being normal later, will be described.
The data structure of the SDL 1501 shown in part (a) of FIG. 16 is the same as that shown in FIG. 15. In part (a) of FIG. 16, the content of the first update information 1504 and the second update information 1510 are both M, and the registered defect number 1505 is 2.
Part (b) of FIG. 16 shows a post-update data structure of the SDL 1501 in the case where the SDL 1501 is updated normally. The content of the first update information 1504 is updated from M to M+1. The registered defect number 1505 is updated from 2 to 1. The position information of the defect sector which has been determined as being normal (second defect position information 1508) and the position information of the substitute sector for substituting that sector (second substitute position information 1509) are deleted. Thus, the first defect position information 1506 and the first defect position information 1507 are left. The content of the second update information 1510 is updated from M to M+1, like the first update information 1504. The second update information 1510 is located subsequent to the first substitute position information 1507. The unused field 1511 is increased by the size corresponding to the second defect position information 1508 and the second substitute position information 1509 which have been deleted.
Part (c) of FIG. 16 shows a post-update data structure of the SDL 1501 in the case where the SDL 1501 is not updated normally. It is assumed that immediately after the registered defect number 1505 is updated, the disc drive apparatus is turned off. In this case, the first update information 1504 and the registered defect number 1505 are updated normally as in part (b) of FIG. 16. However, the second defect position information 1508, the second substitute position information 1509, the second update information 1510 and the unused field 1511 remain the same as those in the pre-update data structure shown in part (a) of FIG. 16.
In the case of the data structure shown in part (c) of FIG. 16, determination on the update result is performed. The disc drive apparatus uses, for example, the updated registered defect number 1505 to read the second defect position information 1508 as the second update information 1510. The disc drive apparatus compares the content of the first update information 1504 and the content of the second defect position information 1508 read as the second update information 1510. When the content of the first update information 1504 and the content of the second defect position information 1508 unfortunately match each other, the disc drive apparatus determines that the SDL 1501 has been updated normally even though the updating of the SDL 1501 was a failure.
In the case where the information recording medium 1500 shown in FIG. 15 considers error correction of the size of 1ECC and the size of the SDL 1501 does not exceed 1ECC size, the problem described above with reference to part (c) of FIG. 16 does not occur. However, when the size of the SDL 1501 exceeds 1ECC size, the above-described problem occurs.